1. Field of the Disclosure
This disclosure relates generally to a semiconductor optical amplifier and, more particularly, to a semiconductor slab optical amplifier that includes gain layers at upper and lower surfaces of the slab and includes edge photo-pumping along the length of one or more of the four side surfaces of the slab.
2. Discussion of the Related Art
A semiconductor gain medium may be the most efficient optical medium known. Electrically pumped diode lasers have achieved an electrical-to-optical efficiency as high as 73% at room temperature and above 85% at 80K. In addition, semiconductor lasers can be photo-pumped using other lasers, where the benefit includes using low brightness pump power to achieve high brightness output beams. This is in contrast to solid lasers, such as YAG lasers, whose efficiency is typically in the region of 10-30%.
One known photo-pumped laser is a vertical cavity surface emitting laser (VCSEL). When a VCSEL is pumped by electrical injection, it is limited in output power to less than 1 watt. However, photo-pumped VCSELs have been shown to provide beam output power at about 20 watts. A typical VCSEL includes a resonate periodic gain (RPG) structure in which quantum wells (QW) are positioned at the anti-nodes (maxima) of a standing wave pattern in the VCSEL that is formed when forward and backward laser beams overlap as is typically done in an optical resonator or slab amplifier. These RPG structures can provide enhanced gain for the signal wavelength when photo-pumped at a wavelength absorbed by the quantum wells or the surrounding barrier material.